Considerable effort and multiple schemes have been devised in an attempt to reduce exhaust emissions from compression ignition (e.g. internal combustion) engines operating on middle distillate fuels. Exhaust emissions are produced by burning fuel in the engine and are emitted through an exhaust system from the engine. A majority of the emissions include hydrocarbons, which are unburned or partially burned fuels, nitrogen oxides (NOX) which are generated when nitrogen in the air reacts with oxygen under the high temperature and pressure conditions inside the engine, carbon monoxide (CO) which is a product of incomplete combustion, particulates, and carbon dioxide (CO2) which is a product of the complete combustion of hydrocarbons.
In an attempt to reduce emissions, components may be added to the fuel that may be effective for reducing one or more of hydrocarbons, NOX, CO, and particulates. However, diesel fuels present a particularly difficult emissions problem because of the need to simultaneously reduce both particulate and NOX emissions. For example, additives which lower particulate emissions may increase NOX emissions, and vice versa. Accordingly, it would be desirable to provide additives for diesel fuels that are effective for lowering NOX emissions without adversely affecting the amount of particulate emissions emitted from the engine.
With regard to the foregoing, embodiments of the disclosure provide a fuel additive and method for reducing emissions from an engine combusting a middle distillate fuel. The fuel additive contains a synergistic combination of (a) a cetane improver and (b) a mineral oil co-additive.
In an exemplary embodiment, the disclosure provides a method for reducing NOX emissions from an engine exhaust for an engine combusting a middle distillate fuel. The method includes the steps of incorporating in a middle distillate fuel an amount of a synergistic combination of (a) an alkyl nitrate ester and (b) a mineral oil co-additive.
Another exemplary embodiment of the disclosure provides an additive package for a middle distillate fuel. The additive package includes (a) an alkyl nitrate ester and (b) a mineral oil co-additive. A volume ratio of (a) to (b) in the additive package ranges from about 1:1 to about 30:1.
An advantage of the disclosed embodiments is that the additive package described herein may exhibit an unexpected synergistic decrease in NOX emissions from the combusting of a middle distillate fuel, compared to other additives and additive combinations. Furthermore, the additive package may not exhibit an adverse increase in particulate emissions compared to other additives used to improve NOX emissions. Other benefits and advantages may be apparent from the following detailed description and examples.